U.S. patent number 7,253,252 [Application Number 11/178,708] was granted by the patent office on 2007-08-07 for water-soluble aspartate.
This patent grant is currently assigned to Bayer MaterialScience AG. Invention is credited to Burkhard Kohler, Meike Niesten, Joachim Simon, Christian Wamprecht.
United States Patent |
7,253,252 |
Kohler , et al. |
August 7, 2007 |
Water-soluble aspartate
Abstract
The present invention relates to new water-soluble polyaspartic
esters and also to their use in aqueous coating compositions.
Inventors: |
Kohler; Burkhard (Leverkusen,
DE), Niesten; Meike (Koln, DE), Simon;
Joachim (Dusseldorf, DE), Wamprecht; Christian
(Neuss, DE) |
Assignee: |
Bayer MaterialScience AG
(Leverkusen, DE)
|
Family
ID: |
35005720 |
Appl.
No.: |
11/178,708 |
Filed: |
July 11, 2005 |
Prior Publication Data
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Document
Identifier |
Publication Date |
|
US 20060014922 A1 |
Jan 19, 2006 |
|
Foreign Application Priority Data
|
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Jul 15, 2004 [DE] |
|
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10 2004 034 271 |
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Current U.S.
Class: |
528/328; 510/434;
528/310; 528/44; 528/59; 528/61 |
Current CPC
Class: |
C07C
229/24 (20130101); C08G 18/3821 (20130101); C09D
175/02 (20130101) |
Current International
Class: |
C08G
69/10 (20060101) |
Field of
Search: |
;510/434
;528/44,59,61,310,328 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Boykin; Terressa
Attorney, Agent or Firm: Gil; Joseph C. Whalen; Lyndanne
M.
Claims
What is claimed is:
1. Hydrophilic polyaspartic esters of the general formula (I)
##STR00008## where R is C.sub.1-C.sub.4 alkyl radical, A and A'
independently of one another are hydrogen or methyl, X is an
n-valent aliphatic, araliphatic or cycloaliphatic radical having 1
to 20 carbon atoms and optionally containing ether bridges, l and m
are natural numbers from 0 to 10 whose sum l+m=1 to 20, and n is a
natural number from 1 to 3.
2. Hydrophilic polyaspartic esters according to claim 1, wherein A
and A' are hydrogen, X is an n-valent aliphatic or cycloaliphatic
radical having 1 to 10 carbon atoms and optionally containing ether
groups, and l and m independently of one another are 1, 2 or 3.
3. Hydrophilic polyaspartic esters according to claim 1 having
number-average molecular weights of 300 to 1000 g/mol.
4. Hydrophilic polyaspartic esters according to claim 1, having
viscosities at 23.degree. C. of 50 to 5000 mPas.
5. Aqueous solutions or dispersions comprising hydrophilic
polyaspartic esters according to claim 1.
6. Aqueous solutions or dispersions according to claim 5, wherein
the polyaspartic ester contents are from 30% to 95% by weight.
7. Process for preparing hydrophilic polyaspartic esters comprising
reacting maleic esters of the general formula (II) ##STR00009##
where R is a C.sub.1-C.sub.4 alkyl radical, A and A' independently
of one another are hydrogen or methyl, and l and m independently of
one another are natural numbers from 0 to 10 and their sum l+m=1 to
20 with an n-valent amine of the formula (III) ##STR00010## where X
is an n-valent aliphatic, araliphatic or cycloaliphatic radical
having 1 to 20 carbon atoms and optionally containing ether bridges
and n is a natural number from 1 to 3 at temperatures of 0 to
100.degree. C., preferably of 15 to 50.degree. C.
8. A two-component coating composition comprising a) at least one
hydrophilic polyaspartic ester according to claim 1, b water, c) at
least one polyisocyanate and d) optionally auxiliaries and
additives.
9. Coatings comprising polyaspartic esters according to claim
1.
10. Substrates coated with coatings according to claim 9.
11. The process of claim 7, wherein the process is carried out in
the absence of solvent.
Description
CROSS REFERENCE TO RELATED APPLICATION
This application claims priority under 35 U.S.C. .sctn.119 to
German patent application DE 10 2004 034 271.7, filed Jul. 15,
2004.
FIELD OF THE INVENTION
The present invention relates to new water-soluble polyaspartic
esters and also to their use as aqueous coating compositions.
BACKGROUND OF THE INVENTION
Two-component coating compositions comprising a polyisocyanate
component binder in combination with a reactive component that is
reactive toward isocyanate groups, in particular a polyhydroxyl
component, have long been known. They are suitable for producing
high-grade coatings, which can be made hard, elastic,
abrasion-resistant and solvent-resistant.
In view of the fact that primary amines undergo a spontaneous and
rapidly uncontrollable reaction with polyisocyanates they are
unsuitable as reaction partners for polyisocyanates in
two-component coatings.
EP-A 0 403 921 describes low-viscosity polyaspartic esters which
contain secondary amino groups and whose reactivity towards NCO
groups is therefore moderate as compared with primary amines.
Polyaspartic esters of this kind are particularly suitable for
preparing low-solvent or solvent-free coating compositions which
exhibit rapid curing.
Polyaspartic esters of this kind are, however, not water-soluble or
water-dispersible, and so are not suitable for use in aqueous
binders.
In view of the evermore stringent legislation governing permitted
levels of volatile organic components in, for example, coating
compositions, there is increasing demand for aqueous systems.
Aqueous two-component coating compositions have been known for
years and are described for example in EP-A 0 358 979.
EP-B 0 818 492 describes aqueous secondary polyamines which are
obtained by Michael Addition of polyamines with oligoesters
containing maleic ester units. A disadvantage of such products is
that reaction of the polyisocyanate may be followed by the
formation of hydantoin, as a result of which the oligoester chains
are cleaved. This in turn leads to a loss of mechanical properties
on the part of the coating.
EP-A 0 849 301 describes aqueous binder mixtures based on
polyaspartic esters and aqueous polyisocyanates. A disadvantage,
however, is that these polyaspartic esters are not
water-dispersible or water-soluble, and so cannot be provided in
the form of storage-stable aqueous formulations. The coatings must
therefore be produced by adding the aqueous polyisocyanate to the
hydrophobic polyaspartic ester, then mixing the system with water
and applying it immediately.
For reasons of improved processing, however, it would be desirable
to be able to use water-soluble or water-dispersible aspartates or
aqueous formulations thereof in such systems.
SUMMARY OF THE INVENTION
An object of this invention was therefore to provide water-soluble
polyaspartic esters for preparing aqueous two-component (2K)
coating compositions for producing polyurea coatings and/or
polyurea-polyurethane coatings.
It has now been found that water-soluble polyaspartic esters can be
prepared by reacting amines with maleic esters containing one or
more ethylene oxide units. The invention accordingly provides
hydrophilic polyaspartic esters of the general formula (I),
##STR00001## where R is a C.sub.1-C.sub.4 alkyl radical, A and A'
independently of one another are hydrogen or methyl, X is an
n-valent aliphatic, araliphatic or cycloaliphatic radical having 1
to 20 carbon atoms and optionally containing ether bridges, l and m
are natural numbers from 0 to 10 whose sum l+m=1 to 20, and n is a
natural number from 1 to 3.
The invention further provides a process for preparing the
polyaspartic esters of the invention, in which maleic esters of the
general formula (II),
##STR00002## are reacted with an n-valent amine of the formula
(III),
##STR00003## at temperatures of 0 to 100.degree. C., preferably of
15 to 50.degree. C., preferably without solvent.
The meaning of n, X, R, A, A', l and m corresponds to the
definitions indicated above for formula (I).
The invention accordingly further provides aqueous solutions or
dispersions comprising the polyaspartic esters of the
invention.
Likewise provided for the present invention are two-component (2K)
coating compositions for preparing polyurethane-polyurea coatings,
comprising at least one hydrophilic polyaspartic ester of the
formula (I) according to the invention, water, at least one
polyisocyanate and optionally auxiliaries and additives.
DETAILED DESCRIPTION OF THE INVENTION
The invention accordingly provides hydrophilic polyaspartic esters
of the general formula (I),
##STR00004## where R is a C.sub.1-C.sub.4 alkyl radical, A and A'
in dependently of one another are hydrogen or methyl, X is an
n-valent aliphatic, araliphatic or cycloaliphatic radical having 1
to 20 carbon atoms and optionally containing ether bridges, l and m
are natural numbers from 0 to 10 whose sum l+m=1 to 20, and n is a
natural number from 1 to 3.
Preferably A and A' are hydrogen.
Preferably X is an n-valent aliphatic or cycloaliphatic radical
having 1 to 10 carbon atoms and optionally containing ether
bridges.
Preferably l and m independently of one another are natural numbers
from 1 to 3. Preferably the sum of 1+m=2 to 6.
Typically the polyaspartic esters of the invention have
number-average molecular weights of 300 g/mol to 1000 g/mol,
preferably 400 g/mol to 750 g/mol.
Typically the polyaspartic esters of the invention have viscosities
(measured with a rotational viscometer) at 23.degree. C. of 50 to
5000 mPas, preferably 50 to 2500 mPas. With particular advantage
the polyaspartic esters of the invention are soluble in water even
without neutralization (complete or partial protonation of the
amino functions present).
The invention further provides a process for preparing the
polyaspartic esters of the invention, in which maleic esters of the
general formula (II),
##STR00005## are reacted with an n-valent amine of the formula
(III),
##STR00006## at temperatures of 0 to 100.degree. C., preferably of
15 to 50.degree. C., preferably without solvent.
The meaning of n, X, R, A, A', l and m corresponds to the
definitions indicated above for formula (I).
Amines of the formula (II) used with particular preference are
1,2-ethylenediamine, 1,2-diaminopropane, 1,4-diaminobutane,
1,6-diaminohexane, 2,5-diamino-2,5-dimethylhexane, 2,2,4- and/or
2,4,4-trimethyl-1,6-diaminohexane, 1,11-diaminoundecane,
1,12-diaminododecane, 4-aminoethyl-1,8-diaminooctane,
1-amino-3,3,5-trimethyl-5-aminomethylcyclohexane, 2,4- and/or
2,6-hexahydrotolylenediamine, 2,4'- and/or
4,4'-diaminodicyclohexylmethane,
3,3'-dimethyl-4,4'-diaminodicyclohexylmethane,
2,4,4'-triamino-5-methyldicyclohexylmethane and polyether
polyamines having aliphatically attached primary amino groups and a
number-average molecular weight M.sub.n of 148 to 6000 g/mol is
obtained.
The maleic esters of the formula (II) are obtainable by complete or
partial transesterification of maleic esters with
monohydroxy-functional ethers.
Preferred maleic esters used are dimethyl maleate, diethyl maleate,
dipropyl maleate, diisopropyl maleate, dibutyl maleate,
di-tert-butyl maleate, di-sec-butyl maleate or diisobutyl maleate.
Particular preference is given to dimethyl maleate or diethyl
maleate, very particular preference to dimethyl maleate.
The monohydroxy-functional ethers correspond to the formula
(IV),
##STR00007## where
R and m have the definition laid down in connection with formula
(I).
Ethers of the formula (IV) used are preferably ethylene glycol
monomethyl ether, diethylene glycol monomethyl ether or triethylene
glycol monomethyl ether.
The reactants are reacted typically in a molar ratio of 1:10 to 4:1
(maleic ester to alcohol of the formula (IV)) at temperatures of
100 to 200.degree. C., preferably of 120 to 160.degree. C. in the
presence of catalysts.
Catalysts used are typically compounds based on tin, titanium,
alkali metals or alkaline earth metals. Preferred catalysts are
tin-based compounds such as dibutyltin oxide or dibutyltin
dilaurate, for example.
In order to shift the equilibrium the alcohol liberated during the
transesterification is preferably removed by distillation. The
progress of the reaction can be monitored on the basis of the
amount of alcohol removed by distillation. The reaction is
typically continued until the theoretically calculated amount of
alcohol has been distilled off.
In the case where the ether of the formula (IV) has been used in
excess amount relative to the sum of the ester functions present,
it too may be distilled off after the end of the
transesterification.
The resultant maleic esters of the formula (II) are then used,
preferably without a further purification step, in the reaction to
give the polyaspartic ester. Distillative purification can take
place in principle, but should be carried out only in the case of
those products which have molar weights of below 300 g/mol, since
otherwise distillation may be accompanied by product
decomposition.
Another way of preparing the maleic esters of the formula (II) is
to react maleic anhydride with ethers of the formula (IV),
operating at temperatures of 80 to 160.degree. C. and removing the
water of reaction by means of suitable distillation techniques.
Additionally use is made as well of acidic catalysts such as
sulphuric acid, p-toluenesulphonic acid or acidic ion
exchangers.
This way is employed in particular when ethylene glycol monoalkyl
ether is used for ether of the formula (IV).
The hydrophilic polyaspartic esters of the invention can be
resolved without problems in water or formulated without problems
as stable dispersions. For this purpose it is commonly enough to
mix the ester with water, although the use, if desired, of
mechanical assistants such as high-speed stirrers or dispersers is
also possible.
Such dispersions or solutions typically have concentrations, based
on the polyaspartic ester, of 30% to 95% by weight, preferably 50%
to 90% by weight.
The invention accordingly further provides aqueous solutions or
dispersions comprising the polyaspartic esters of the
invention.
Likewise provided for the present invention are two-component (2K)
coating compositions for preparing polyurethane-polyurea coatings,
comprising a) at least one hydrophilic polyaspartic ester of the
formula (I) according to the invention, b) water, c) at least one
polyisocyanate and d) optionally auxiliaries and additives.
The NCO:NH equivalent ratio is typically 0.5:1 to 3.0:1, preferably
0.8:1 to 2.5:1.
Suitable polyisocyanates of component c) are organic
polyisocyanates having an average NCO functionality of at least 2
and a molecular weight of at least 140 g/mol. Of particularly high
suitability are (i) unmodified organic polyisocyanates of the
number-average molecular weight range from 140 to 300 g/mol, (ii)
paint polyisocyanates with a number-average molecular weight of 300
to 1000 g/mol, and (iii) NCO prepolymers containing urethane groups
and having number-average molecular weights>1000 g/mol, or
mixtures of (i) to (iii).
Examples of polyisocyanates of group (i) are
1,4-diisocyanatobutane, 1,6-diisocyanatohexane (HDI),
1,5-diisocyanato-2,2-dimethylpentane, 2,2,4- and
2,4,4-trimethyl-1,6-diisocyanatohexane,
1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI),
1-isocyanato-1-methyl-4(3)-isocyanatomethylcyclohexane,
bis(4-isocyanatocyclohexyl)methane, 1,10-diisocyanatodecane,
1,12-diisocyanatododecane, cyclohexane 1,3- and 1,4-diisocyanate,
xylylene diisocyanate isomers, triisocyanatononane (TIN),
2,4-diisocyanatotoluene or its mixtures with
2,6-diisocyanatotoluene with, preferably, based on mixtures, up to
35% by weight 2,6-diisocyanatotoluene, 2,2'-, 2,4'-,
4,4'-diisocyanatodiphenylmethane or technical polyisocyanate
mixtures of the diphenylmethane series or any desired mixtures of
the isocyanates mentioned.
Polyisocyanates of group (ii) are the paint polyisocyanates that
are known per se. The term "paint polyisocyanates" comprehends, for
the purposes of the invention, compounds or mixtures of compounds
which are obtained by conventional oligomerization reaction of
simple diisocyanates of the type exemplified under (i).
Examples of suitable oligomerization reactions are
carbodiimidization, dimerization, trimerization, biuretization,
urea formation, urethanization, allophanatization and/or
cyclization with the formation of oxadiazine structures. Often in
the course of "oligomerization" two or more of the said reactions
proceed simultaneously or in succession.
Preferably the "paint polyisocyanates" (ii) comprise biuret
polyisocyanates, polyisocyanates containing isocyanurate groups,
polyisocyanate mixtures containing isocyanurate groups and
uretdione groups, polyisocyanates containing urethane and/or
allophanate groups, or polyisocyanate mixtures containing
isocyanurate and allophanate groups, said polyisocyanate mixtures
being based on simple diisocyanates.
The preparation of such paint polyisocyanates is known and is
described for example in DE-A 1 595 273, DE-A 3 700 209 and DE-A 3
900 053 or in EP-A-0 330 966, EP-A 0 259 233, EP-A-0 377 177,
EP-A-0 496 208, EP-A-0 524 501 or U.S. Pat. No. 4,385,171.
Polyisocyanates of group (iii) are the prepolymers that are known
per se and contain isocyanate groups and are based on simple
diisocyanates of the type exemplified above and/or are based on
paint polyisocyanates (ii) on the one hand and organic polyhydroxy
compounds having a number-average molecular weight of more than 300
g/mol on the other. While the paint polyisocyanates of group (ii)
that contain urethane groups are derivatives of low molecular
weight polyols, of the number-average molecular weight range from
62 to 300 g/mol, examples of suitable polyols being ethylene
glycol, propylene glycol, trimethylolpropane, glycerol or mixtures
of these alcohols, the polyhydroxyl compounds used for preparing
the NCO prepolymers of group (iii) have number-average molecular
weights of more than 300 g/mol, preferably more than 500 g/mol,
more preferably from 500 to 8000 g/mol. Polyhydroxyl compounds of
this kind are in particular those which contain per molecule 2 to
6, preferably 2 to 3, hydroxyl groups and are selected from the
group consisting of ether, ester, thioether, carbonate and
polyacrylate polyols and mixtures of such polyols.
In connection with the preparation of the NCO prepolymers (iii) the
stated higher molecular weight polyols can also be employed in
blends with the stated low molecular mass polyols, so as to result
directly in mixtures of low molecular mass paint polyisocyanates
(ii) containing urethane groups and higher molecular weight NCO
prepolymers (iii), which are likewise suitable as a starting
component (C) according to the invention.
For preparing the NCO prepolymers (iii) or their mixtures with the
paint polyisocyanates (ii), diisocyanates (i) of the type
exemplified above or paint polyisocyanates of the type exemplified
under (ii) are reacted with the higher molecular weight hydroxyl
compounds or their mixtures with low molecular weight polyhydroxyl
compounds of the type exemplified, observing an NCO/OH equivalent
ratio of 1.1:1 to 40:1, preferably 2:1 to 25:1, with the formation
of urethane. Optionally it is possible, when using an excess of
distillable starting diisocyanate, to remove it by distillation
following the reaction, so that monomer-free NCO prepolymers, i.e.
mixtures of starting diisocyanates (i) and true NCO prepolymers
(iii), are present and may likewise be used as component (A).
Low-viscosity, hydrophilicized polyisocyanates having free
isocyanate groups and based on aliphatic, cycloaliphatic,
araliphatic and/or aromatic isocyanates, more preferably aliphatic
or cycloaliphatic isocyanates, can also be employed.
Hydrophilicization of the polyisocyanates is possible, for example,
by reaction with substoichiometric amounts of monofunctional,
hydrophilic polyether alcohols. The preparation of hydrophilicized
polyisocyanates of this kind is described for example in EP-A 0 540
985, p. 3, 1. 55-p. 4, 1. 5. Also highly suitable are the
polyisocyanates containing allophanate groups that are described in
EP-A-959087, p. 3, 1. 39-51 and are prepared by reacting
polyisocyanates of low monomer content with polyethylene oxide
polyether alcohols under allophanatization conditions. Also
suitable are the water-dispersible polyisocyanate mixtures based on
triisocyanatononane that are described in DE-A 100 078 21, p. 2, 1.
66-p. 3, 1. 5, and also polyisocyanates hydrophilicized with ionic
groups (sulphonate groups, phosphonate groups), as described for
example in DE 10024624, p. 3, 1. 13-33. A further possibility is
that of hydrophilicization by addition of commercially customary
emulsifiers.
Also possible in principle, of course, is the use of mixtures of
different polyisocyanates of the aforementioned kind.
Auxiliaries and additives present optionally in component d) are
for example, surface-active substances, abrasive waxes, internal
release agents, fillers, dyes, pigments, flame retardants,
hydrolysis inhibitors, microbicides, flow assistants, antioxidants
such as 2,6-di-tert-butyl-4-methylphenol, UV absorbers of the
2-hydroxyphenylbenzotriazole type or light stabilizers of the type
of the HALS compounds unsubstituted or substituted on the nitrogen
atom, such as Tinuvin.RTM. 292 and Tinuvin.RTM. 770 DF (Ciba
Spezialitaten GmbH, Lampertheim, DE) or other commercially
customary stabilizers, as described for example in
"Lichtschutzmittel fur Lacke" (A. Valet, Vincentz Verlag, Hanover,
1996) and "Stabilization of Polymeric Materials" (H. Zweifel,
Springer Verlag, Berlin, 1997, Appendix 3, pp. 181-213), or any
desired mixtures of these compounds.
Typically when preparing the coating compositions of the invention
the individual components a), b) and optionally d) are mixed with
one another. Subsequently component c, mixed optionally with
further constituents of d), is added and the components are
mixed.
Coating compositions based on the aqueous polyaspartic esters of
the invention can be applied to any desired substrates in
accordance with methods that are known per se, such as by spraying,
spreading, flow coating or by means of rollers or doctor blades,
for example. Examples of suitable substrates include metal, wood,
glass, stone, ceramic materials, concrete, rigid and flexible
plastics, textiles, leather or paper.
Curing can be performed at room temperature or at elevated
temperature.
EXAMPLES
Unless noted otherwise, all percentages are by weight.
The pendulum hardnesses were determined by the method of Konig, DIN
53157.
The dynamic viscosities were determined at 23.degree. C. using a
rotational viscometer (ViscoTester.RTM. 550, Thermo Haake GmbH,
D-76227 Karlsruhe).
The OH number was determined in accordance with DIN 53240 T.2.
Polyisocyanate 1
Bayhydur.RTM. 3100 (commercial product of Bayer MaterialScience AG,
Leverkusen, DE), hydrophilic aliphatic polyisocyanate based on
hexane 1,6-diisocyanate, having an NCO content of 17.4% by weight
and a viscosity at 23.degree. C. of 2800 mPas.
Polyisocyanate 2
Desmodur.RTM. N3400 (commercial product of Bayer MaterialScience
AG, Leverkusen, DE), aliphatic polyisocyanate based on hexane
1,6-diisocyanate, having an NCO content of 21.8% by weight and a
viscosity at 23.degree. C. of 150 mPas.
Hydrophobic Polyaspartic Ester
Desmophen.RTM. NH1420 (commercial product of Bayer MaterialScience
AG, Leverkusen, DE), polyaspartic ester based on
4,4'-diaminodicyclohexylmethane and diethyl maleate.
Preparation of the Hydrophilic Maleic Ester
432 g of dimethyl maleate, 493 g of triethylene glycol monomethyl
ether and 0.9 g of dibutyltin oxide were weighed out into a
three-necked flask with stirrer, distillation column and
thermometer and the mixture was heated to 140.degree. C. In
parallel with the ensuing transesterification reaction the methanol
liberated was distilled off under vacuum (30 mbar). After the
theoretical amount of 96 g of methanol had distilled over, the
reaction was terminated. The resulting product had an OH number of
0.
Preparation of the Hydrophilic Polyaspartic Ester
131 g of 4,4'-diaminodicyclohexylmethane were charged to a
three-necked flask with stirrer, distillation column, thermometer
and nitrogen blanketing and this initial charge was heated to
50.degree. C. Subsequently 345 g of the above-prepared maleic ester
were added dropwise at a rate such that the temperature did not
exceed 50.degree. C. When addition was at an end the temperature
was raised to 60.degree. C. and stirring was continued for 24
hours. The product had a viscosity at 23.degree. C. of 1390
mPas.
Water could be added to prepare aqueous solutions of this
polyaspartic ester. A 50% strength by weight solution in water had
a viscosity at 23.degree. C. of 25 mPas and an 80% strength by
weight solution had a viscosity at 23.degree. C. of 270 mPas.
Preparation of Coating Materials
The hydrophilic polyaspartic ester was dissolved in water in
accordance with the table below and admixed with the stated amount
of the polyisocyanate, with stirring. Subsequently this binder
mixture was applied to a glass plate using a 180 .mu.m drawdown
frame and was cured at room temperature for 24 hours. In the case
of the hydrophilic polyaspartic ester of the invention, clear,
elastic films were obtained. Since the hydrophobic polyaspartic
ester used by way of comparison was not soluble in water, it was
not possible to obtain a homogeneous aqueous solution. Because of
phase separation of the components, this resulted in films which
were unusable.
TABLE-US-00001 TABLE 1 Composition and properties of the coating
materials (amounts in parts by weight) Example 1 2 3 4 4
Hydrophilic polyaspartic ester 80 80 50 80 80 Hydrophobic
polyaspartic ester -- -- -- -- -- Water 20 20 50 20 20
Polyisocyanate 1 50 100 63 40 80 Polyisocyanate 2 -- -- -- -- --
Appearance of film clear clear clear clear clear Pendulum hardness
after 7 days 14 s 31 s 21 s 10 s 13 s
Although the invention has been described in detail in the
foregoing for the purpose of illustration, it is to be understood
that such detail is solely for that purpose and that variations can
be made therein by those skilled in the art without departing from
the spirit and scope of the invention except as it may be limited
by the claims.
* * * * *